Adrien Di Mascio <Adrien.DiMascio@logilab.fr> [Wed, 25 Nov 2015 10:19:52 +0100] rev 10929
[dataimport] fix db-namespace default value handling
In a fresh new instance, the "db-namespace" option is set as empty
by default in the "sources" file.
This seems correct but empty string is not a valid pg_schema and
actually means that we should use "public"